I see enemy mages use them all the time, but i don't use them in combat at all; they use up too much magicka, and furthermore if the ward breaks you get staggered. Not to mention there's a charging time, which means you'd probably have to ward for the entire duration of combat so as to not have a weak ward when fireballs are smashing your way.
so thats my view, perhaps some ward user could enlighten me on the usefulness of wards
